A method of analyzing elements configuring a material has already been researched and developed over a long time in one field of chemistry, which is referred to as analytical chemistry, in addition to methods of quantifying elements by a number of analysis methods and analysis apparatuses.
As a quantification method for an element which has been currently and mainly used, there are fluorescence spectroscopy, atomic absorption spectroscopy (AAS), X-ray fluorescence (XRF), inductively coupled plasma-atomic emission spectrometry (ICP-AES), instrumental neutron activation analysis (INAA), and the like. In describing the various methods below, the AAS has a relatively slow analysis speed, and may be seriously disturbed by medium since it is not capable of performing a multi-element simultaneous analysis. The ICP-AES is capable of detecting multi-elements at the same time, analyzing most of the elements at a sensitivity of about tens of μg/kg (ppb), but has relatively severe spectral interference. The XRF is capable of analyzing many elements at the same time and is possible to perform non-destructive analysis in a case of a metal sample or a powder sample, but merely has a detection limit in a unit of about mg/kg (ppm). The INNA has advantages in that sensitivity is high and multi-element simultaneous analysis by a non-destructive method is possibly performed, but has a disadvantage in that it is difficult to be used since a large size of neutron source such as a nuclear reactor and radiation detection apparatuses are required.
The ICP-MS is capable of rapidly and accurately analyzing elements present in a liquid sample up to a level of μg/kg (ppb) to ng/kg (ppt), and has a high sensitivity and a large range for quantification. In addition, since measurement for an isotope ratio is possible, an isotope dilution method may be applied. The isotope dilution method has been used as an analysis method for a trace component in a biological field, an environmental engineering field, a nuclear energy field, and the like. Korean Patent No. 10-0654293 (Patent Document 1) discloses a specialized isotope dilution mass spectrometry of reactive species.
Since isotopes have different mass only, but almost the same physical and chemical properties, they are used as the best internal standard material in analysis of a trace component. Therefore, when enriched stable isotopes with a known amount with respect to an element to be analyzed are put into a sample to allow equilibrium among the isotopes, and then a ratio of the isotopes is measured, quantification is possibly performed regardless of loss in elements to be measured which easily occurs during pretreatment for the target sample for detection. In addition, since a medium effect involved in an analysis process also equally affects, all isotopes, an effect by the medium components on the measurement of the ratio of the isotopes may be reduced under an assumption in which complete equilibrium is achieved. The isotope dilution method may obtain significantly accurate analysis results on elements having two or more stable isotopes to be mainly used for determination of certified values of a certified standard material.
The ICP-MS is a method of high temperature-plasma spraying a sample solution obtained by pretreatment to break up to an atomic unit, followed by ionization, and separation according to difference in mass to charge ratio of ions, to measure a size of ion signal. In the ICP-MS, even though considerable time and effort are required for pretreatment for the target sample, 20 kinds or more of elements are capable of being simultaneously measured, and detection limit of the device is significantly low, such that traces of harmful elements present in the sample are possibly measured, and stable measurement values in view of reproducibility and reliability of the measurement values are provided as compared to the other existing measurement methods. However, to do this, significantly considerable efforts are needed in the pretreatment of the sample. The pretreatment of the sample for ICP-MS measurement mainly uses an acid decomposition including a heating process by using strong acid, wherein different kinds of acids and optimized heating time are required for each sample. For example, in a case of a plastic sample, or the like, which is difficult to decompose, several hours or more of heating time using dangerous concentrated nitric acid and concentrated sulfuric acid are required in some cases. In this process, due to incomplete decomposition of the sample or remaining sulfuric acid, spray efficiency of the sample solution is not good, which causes a negative influence on the measurement results. In addition, in volatile elements such as arsenic (As), bromine (Br), chlorine (Cl), and the like, loss in the pretreatment commonly happens, and possibility of pollution during the pretreatment over a long period of time increases, which causes distortion of the measurement results. In order to solve the above-described problems, various researches on the pretreatment method of the sample are required together with methods for increasing accuracy of an inductively coupled plasma mass spectrometry.